Method of calcining alkaline-earth carbonates



Aug. 18, 1925. 1,550,551

' H. MEHNER METHOD OF CALGINING ALKALINE EARTH CARBONATES Original Filed Feb. 14, 1922 Patented Aug. 18, 1925.

UNITED STATES HERMANN MEHNER, BERLIN-CHARLOTTENBURG, GERMANY.

METHOD OF CALCINING- ALKALINE-EARTH CARBONATES.

Original application filed February 14, 1822, Serial No. 536,569. Divided and this application filed April 10, 1925. Serial No. 22,210.

To all whom it may concern:

Be 1t known that I, HERMANN MEHNER, a citizen of the German Republic, residing at Berlin-Charlottenburg, Germany, have invented certain new and useful Improvements in Methods of Calcining Alkaline- Earth carbonates, of which the following is a specification.

This invention is a division of application bearing Serial No. 536,569, filed February 14th, 1922, and relates to a method or process of calcining alkaline earth carbonates in a furnace-generator wherein a source of heat produced above a charge maintained on a pervious grate is caused to radiate its heating energy upon the material to be treated, a gaseous intermediate layer separating the flames and the products of combustion, the volatile reaction products being led away through the pervious grate and afterwards away from the generator.

My improved process is particularly applicable to the production of calcium carbonate by calcination of alkaline earth carbonates in a furnace-generator by feeding heating gases over a charge therein and in causing combustion of the gases by the admission of air into the upper portion of the furnace-generator through a pervious arch thereof, and alsothrough a filling of heat retaining material, and in providing means whereby the products of combustion may be withdrawn from the furnace-generator continuously through its top, and when free from carbon or the like the heat will be radiated upon a charge on the pervious grate and the gaseous product-s of calcination off the material on the grate will be drawn out of a space in the furnace-generator below said pervious grate.

In carrying out my process, the relatively cool gases used for calcining the material are admitted above the charge and form an intermediate protecting layer between the charge and the burning gases whereby the flames caused by the combustion of the gases will be remote from the charge, the main consumption taking place immediately below the arch or upper portion of the furnacegenerator and being radiated upon the charge maintained upon the pervious grate.

When employing my process for burning limestone or calcining alkaline earth carbonates according to my invention, the combustible gases are admitted directly above initial flames produced are kept away from the charge, the generated heat being radiated from the combustion Zone upon the charge through this protecting gaseous layer. The mat passes down through the charge and out of the furnace-generator with the prod- I nets of calcination. A great saving of heat is effected by passing air into the upper zone of the furnace-generator and then radiating the heat from the upper Zone oi the furnacegenerator through the intermediate zone and upon the charge maintained on the pervious boniterous material.

In the accompanying drawlng which illustrates my invention,-

Figure 1 is a cross section of a furnacegenerator constructed to accord with my invention; and

Figure 2 is a longitudinal section.

The furnace-generator is provided with an arch l of pervious material which may be unglazed fire brick or the like, and below the arch. are the usual walls which carry a grate of pervious material upon which the charge is placed, andbelow said grate is aspace having an outlet 6 with a damper or controlling means '7. The arch of the furnace-generator is provided with an opening t leading into a chimney and provided with a damper or controlling means of usual construction.

The furnace-generator is also provided with hoppers 8 which communicate with passages through the arch, the charge being fed upon the grate 2 through said hoppers. The arch 1 is provided with a filling 22 of suitable heat retaining pervious material, for instance, broken stone, and said filling is separated from the vertical walls of the furnace by angle irons or plates 5. The entire grate, which charge contains lime and car- Iurnace-generator is encased by a sheet metal covering 2t, said covering or casing having an opening 25, through which air is admitted to the filling 22 and is passed therefrom throng-lithe pervious arch 1 and into the upper zone or the-furnace-generator, in which zone the combustion of the flame gases is consumed along with the heated air which is passed into the atoresaid upper zene ot the furnace-generator.

Below what may be considered the upper combustion zone 01 the furnace-generator there are openings 3 and 3, through which relatively cool combustible gases and steam may be admitted into the furnace-generator above the charge placed upon the pervious grate. The products of reaction are passed downwardly throughthe pervious grate into as ace below said grate, from whence they are discharged or drawn out of the furnacegenerator by way-of valved openings 6 having valves or dampers 7.

lVhen applying the furnace-generator herein'shown for burning limestone or carrying out other calcinations, the furnacegenerator is charged with limestone placed upon the grate, and into this charge, steam or water vapor is fed in an appropriate manner, as through the openings 3 and 3. The resulting carbon dioxide, or other products which are dissociated from the material placed upon the grate are discharged downward into the space below the under side of the grate and are withdrawn by suction through the openings 6.

By the manner of utilizingthe heat generated within the furnace from limestone may be produced pure lime, carbon dioxide for industrial purposes which will be free from nitrogen, and a lime whiehis tree from bitumen. The carbon dioxide may be used For the aeration of beverages and for other industrial purposes.

The simultaneous use 01 water vapor or steam, heated air and a gaseous fuel to produce combustion in the treatment of material from which lime may be produced by burning, and by the action of fluid liquid upon the lime, produces carbondioxide and water vapor, which together have atmospheric pressure, and consequently to discharge them from the turnacegenerator the pressure therein will have to be in excess of the atmosphere, or the exhaust will have to be supplied with exhaust means.

I claim 1. The process of calcining alkaline earth carbonates i-n afurnaeegenerater to produce time which consists in supporting a charge of an alkaline earth carbonate upon a pervious grate maintained-withinthe-lower portion of the turi'iaceegenerator, admitting relatively e001 combustible :gas and steam to a zone immediately above said charge, admitting air into an upper zone of the turnace-generator, said zone constituting a combustion zone wherein the combustible gas is burned and is separated from the char e by the relatively eool'combustible and steam which form an'intermediate layer, radiating-the heat from the combustion zone through said inter-mediate layer above the charge, and drawing oft the products dissociatedfrom-the chargefrom a zone below thegrate.

The iproeess'of calciningcalcium carbonate ina turnaee-gener atorto produce lime and carbon dioxide which consists in supporting a charge or calciuincarbonateupon a pervious grate maintained within the-lower portion or" the turnaeergenerator, admitting relatively cool combustible gas and steam to a 20118 immediately above said charge of calcium carbonate, admitting air into an upper zone of the furnace-generator, said upper zone constituting a combustion zone wherein thecombustiblegas is burned and is separated trom-the'charge bythe admitted relatively cool combustible gas and the steam, forming an intermediate layer, radiating the heat of said combustion zone through said steam and combustible gas zone upon thecharge of calcium carbonate. in order to calcinethe same, and then-separating thelime and carbon dioxide by withdrawing the carbon dioxide from i the space below theg'rate.

l-n' testimony whereof I allix my signature this 1 6th dayo t- March, '1925.

*H'ERMANN MEHNER. 

